1. Field of the Invention
The present invention relates to an information processing system including an isochronous transfer serial bus capable of transmitting a plurality of types of packets discriminated by channels, and at least two information processing apparatuses each of which uses the isochronous transfer serial bus as a communication interface and can receive packets of channels assigned to itself, a control method for the information processing system, and an information processing apparatus.
2. Description of the Related Art
Recently, high-speed serial communication interfaces having a function of ensuring a given data transfer rate using a transfer mode such as an isochronous transfer mode (to be referred to as an Iso transfer mode), are receiving a great deal of attention as isochronous transfer serial buses. Known examples of such interface having the Iso transfer mode to transfer data in real time at a high speed are the USB bus and IEEE 1394 bus.
In the Iso transfer mode, each information processing apparatus connected to a bus can be allocated at every prescribed cycle time a necessary number of channels capable of transferring data. This can realize an information processing system for transferring data from a scanning apparatus such as a scanner to a computer or from a computer to a printing apparatus such as a printer, while conforming to a predetermined data transfer rate corresponding to the performance of the apparatus.
In the prior art, however, the number of channels capable of transferring data without fail every prescribed cycle time is limited. If a given apparatus has been allocated channels, another apparatus may not be able to allocate a necessary number of channels simultaneously.
The present invention has been made to overcome the conventional drawbacks, and has as its object to provide an information processing system capable of flexibly assigning channels in an isochronous transfer serial bus to transfer information desired by the user, a control method for the information processing system, and an information processing apparatus.
To achieve the above object, according to the present invention, there is provided an information processing system comprising
an isochronous transfer serial bus capable of transmitting a plurality of types of packets discriminated by channels, and
at least two information processing apparatuses each of which uses the isochronous transfer serial bus as a communication interface and can receive packets of channels assigned thereto,
wherein either one of the information processing apparatuses has channel management means capable of modifying allocation of the channels in accordance with predetermined priority.
When the information processing apparatus which has been allocated channels has low priority, the channel management means preferably assigns the channels allocated by the information processing apparatus to an other information processing apparatus having high priority.
The channel management means preferably stores channel information assigned to each of the information processing apparatuses.
The priority is preferably determined by inputting an operation mode corresponding to which of the information processing apparatuses has operation priority.
The information processing apparatuses preferably include a scanning apparatus and/or printing apparatus.
The channel management means preferably modifies allocation of the channels in accordance with an inquiry from at least one of the information processing apparatuses.
According to the present invention, there is provided an information processing apparatuses which uses, as a communication interface with another apparatus, an isochronous transfer serial bus capable of transmitting a plurality of types of packets discriminated by channels, and can receive packets of channels assigned thereto, comprising
channel management means capable of modifying allocation of the channels in accordance with predetermined priority.
According to the present invention, there is provided a control method for an information processing system having
an isochronous transfer serial bus capable of transmitting a plurality of types of packets discriminated by channels, and
at least two information processing apparatuses each of which uses the isochronous transfer serial bus as a communication interface and can receive packets of channels assigned thereto, comprising
a channel management step for modifying allocation of the channels in accordance with predetermined priority, and
a communication step for performing communication in accordance with allocation of the channels modified in the channel management step.
The channel management step preferably comprises modifying allocation of the channels in accordance with an inquiry from at least one of the information processing apparatuses.
The channel management step preferably comprises
a search step for searching for an available channel in order to allocate the number of channels necessary for a first information processing apparatus of the information processing apparatuses,
a determination step for determining whether any of channels allocated by a second information processing apparatus can be assigned to the first information processing apparatus when no available channel is searched in the search step, and
a channel reallocation step for reassigning at least some of the channels allocated by the second information processing apparatus to the first information processing apparatus when channels assignable to the first information processing apparatus are determined in the determination step to exist in the channels allocated by the second information processing apparatus.
According to the present invention, there is provided a computer-readable memory which stores a control program for an information processing system having
an isochronous transfer serial bus capable of transmitting a plurality of types of packets discriminated by channels, and
at least two information processing apparatuses each of which uses the isochronous transfer serial bus as a communication interface and can receive packets of channels assigned thereto, storing
a code of the channel management program for modifying allocation of the channels in accordance with predetermined priority, and
a code of the communication program for performing communication in accordance with allocation of the channels modified by the channel management program.
The channel management program comprises
a search program for searching for an available channel in order to allocate the number of channels necessary for a first information processing apparatus of the information processing apparatuses,
a determination program for determining whether or not any of channels allocated by a second information processing apparatus can be assigned to the first information processing apparatus when no available channel is searched by the search program, and
a channel reallocation program for reassigning at least some of the channels allocated by the second information processing apparatus to the first information processing apparatus when channels assignable to the first information processing apparatus are determined by the determination program to exist in the channels allocated by the second information processing apparatus.